JP2019081691A - Ceramic reflector, and light source module or rotary body comprising the same - Google Patents

Abstract

To provide a ceramic reflector that has high reflectance while being inexpensive, and a light source module or a rotary body comprising the same.SOLUTION: A ceramic reflection member of the present disclosure contains alumina crystals and composed of alumina-based ceramic including Al of 98 mass% or more in terms of AlO, and its relative density is 92% or more. In equivalent circle diameters of the alumina crystal, diameters less than 0.2 μm are of 3% or more and 15% or less, diameters greater than or equal to 0.2 μm and smaller than or equal to 0.8 μm are of 55% or more and 75% or less, and diameters above 0.8 μm are of 15% or more and 40% or less.SELECTED DRAWING: Figure 1

Description

  The present disclosure relates to a ceramic reflector and a light source module or a rotating body including the same.

  In the headlight for vehicles, in order to improve distance visibility, further high-intensity-ization is calculated | required by light source devices, such as a light emitting diode (LED: Light Emitting Diode) and a semiconductor laser. Along with this, high reflectance is required for members used in the mounting and the periphery of the light source device.

  As a member having such a high reflectance, the applicant has proposed an oxide ceramic containing an alumina crystal and a zirconia crystal (see Patent Document 1).

International Publication 2014/156831

  The oxide ceramics containing alumina crystals and zirconia crystals described in Patent Document 1 have high reflectance such as more than 95%, but they are generally produced using zirconia powder which is more expensive than alumina powder. Since the zirconia powder is added, it becomes expensive.

  In addition, the components used in the mounting of the light source device and in the periphery are required to have mechanical characteristics that can withstand use, including the viewpoint of reliability. Therefore, in the ceramic reflectors, it is required to have high reflectance while having mechanical characteristics that can withstand use while being inexpensive.

  In addition, ceramic reflectors are used, for example, when measuring the rotational speed with a light measuring instrument or the like in rotating bodies such as rotors, shafts, turbines, etc., as applications other than the members used in mounting of light source devices and in the periphery. In order to obtain accurate measurement results, it is required to have high reflectance.

  The present disclosure has been made in view of such circumstances, and is a low-cost ceramic reflector having high reflectance while having mechanical characteristics that can withstand use, and a light source module including the same. The purpose is to provide a rotating body.

The ceramic reflector of the present disclosure is made of an aluminous ceramic that contains alumina crystals and contains 98% by mass or more of Al in terms of Al ₂ O ₃ . And relative density is 92% or more. Further, in the equivalent circle diameter of the alumina crystal, less than 0.2 μm is 3% or more and 15% or less, 0.2 μm or more and 0.8 μm or less is 55% or more and 75% or less, and 0.8 μm or more is 15% More than 40%.

  The light source module of the present disclosure includes the ceramic reflector of the above configuration.

  The rotating body of the present disclosure includes the ceramic reflecting material having the above configuration and a substrate having a color tone different from that of the ceramic reflecting material, and at least a portion of the ceramic reflecting material is exposed on the outer surface side of the substrate. .

  The ceramic reflection member of the present disclosure has high reflectivity while having mechanical characteristics that can be used while being inexpensive.

  The light source module of the present disclosure has high brightness while being reliable.

  The rotating body of the present disclosure can obtain accurate measurement results when measuring the rotation speed and the like using an optical measuring instrument or the like, and is excellent in reliability.

It is a schematic diagram which shows an example of a structure of the light source module of this indication. FIG. 2 is a cross-sectional view showing an example of the configuration of a spherical rotary body and an optical measurement instrument according to the present disclosure.

  The ceramic reflector of the present disclosure will be described.

The ceramic reflector of the present disclosure is made of an aluminous ceramic that contains alumina crystals and contains 98% by mass or more of Al in terms of Al ₂ O ₃ . As described above, since the ceramic reflector of the present disclosure is made of an alumina ceramic containing 98% by mass or more of Al in terms of Al ₂ O ₃ conversion, the ceramic reflector includes the alumina crystal and the zirconia crystal described in Patent Document 1. It is cheaper than oxide ceramics.

The content of the Al in terms _{of Al} 2 _{O 3} performs quantitative analysis of Al using ICP (Inductively Coupled Plasma) emission spectrometer (ICP), may be converted into _Al 2 _{O 3.} Alternatively, qualitative analysis may be performed using a fluorescent X-ray analyzer (XRF), quantitative analysis may be performed on components other than Al using ICP, and the total may be subtracted from 100% by mass.

  And, the ceramic reflector of the present disclosure has a relative density of 92% or more. Therefore, the ceramic reflector of the present disclosure has mechanical properties that can withstand the mounting and peripheral use of the light source device. The relative density can be measured by the Archimedes method.

  In the ceramic reflective material of the present disclosure, the equivalent circle diameter of alumina crystal is less than 0.2 μm but not less than 3% and not more than 15%, and not less than 0.2 μm and not more than 0.8 μm is not less than 55% and not more than 75%. More than 0.8 μm is 15% or more and 40% or less. The equivalent circle diameter means the diameter of a circle when it is replaced with a circle equal to the area when observing an alumina crystal.

  The ceramic reflector of the present disclosure satisfying the above-described configuration has an alumina crystal with a diameter of 0.8 μm or less, which corresponds to a visible light region, with half or more occupied, and an alumina crystal with a large circle equivalent diameter and an alumina crystal with a small circle equivalent diameter Because of the fineness of the alumina-based ceramic, it has a high reflectance. Here, the high reflectance means that the reflectance at 500 nm is 92% or more.

The ceramic reflector of the present disclosure has a relative density of 92% or more, and a reflectance at 500 nm of 92% or more. Although the relative density and the reflectance are generally in a trade-off relationship, since the ceramic reflector of the present disclosure satisfies the above configuration, it has mechanical properties that can withstand use while being inexpensive. It has high reflectance.

  Next, as a measurement method of reflectance, using a spectrocolorimeter (color reader CR-13 manufactured by Konica Minolta), a reference light source D65, a wavelength range of 360 to 740 nm, a visual field of 10 °, and an illumination diameter of 3 × 5 mm The measurement may be performed under conditions, and the value of the reflectance of 500 nm may be read from the measurement result.

  In the ceramic reflector of the present disclosure, the average equivalent circular diameter of alumina crystals may be 0.5 μm or more and 0.7 μm or less. When the average equivalent circle diameter of the alumina crystal is 0.5 μm or more and 0.7 μm or less, the range of the equivalent equivalent circle diameter is in the vicinity of the center value of the visible light region, and thus the reflectance is further increased.

  Here, a method of calculating the number ratio of the equivalent circle diameter of the alumina crystal and the average equivalent circle diameter will be described.

First, the ceramic reflection material is polished and processed into a mirror surface. Then, with the surface polished to a mirror surface as a measurement surface, the measurement surface is observed at a magnification of 5000 using an optical microscope or a scanning electron microscope and photographed with a CCD camera. Next, using the captured image, an image analysis software (Win ROOF Co., Ltd. Mitani Corp.) is used to make the measurement target an area of 413 μm ^{2 and} the equivalent circle diameter of the alumina crystal under the condition without threshold value. taking measurement. And from the circle equivalent diameter of each alumina crystal thus obtained, it is possible to calculate the number ratio and the average circle equivalent diameter for each range of the circle equivalent diameter of the alumina crystal.

  In the ceramic reflector of the present disclosure, the circularity of the alumina crystal may be 0.68 or more and 0.78 or less. Here, the degree of circularity means that when the numerical value is 1 it is a true circle, so the closer to 1 the value gets closer to a true circle, and the value of the degree of circularity indicates the likeness of a circle It is a thing. When the circularity of the alumina crystal is 0.68 or more and 0.78 or less, since the shape is moderately distorted, the gap is small and the density is high, and thus the reflectance is further increased.

  Next, a method of calculating the degree of circularity of alumina crystal will be described.

  First, the ceramic reflection material is polished and processed into a mirror surface. Then, with the surface polished to a mirror surface as a measurement surface, the measurement surface is observed at a magnification of 5000 using an optical microscope or a scanning electron microscope and photographed with a CCD camera. Next, using the captured image, the circularity 1 in the image analysis software "image A (kun) ver 2.52 (registered trademark, manufactured by Asahi Kasei Engineering Co., Ltd.)" is used. As the setting conditions at this time, for example, the lightness is bright, the small figure removal area is 0.002 μm, and the threshold which is an index indicating the brightness of the image is 90 to 120.

  In the ceramic reflector of the present disclosure, the alumina crystal may have a degree of strain in the distribution curve of equivalent circle diameters that is greater than zero. Here, the distribution curve of the circle equivalent diameter is a curve showing the distribution of the circle equivalent diameter of the alumina crystal, with the abscissa of the two-dimensional graph being the circle equivalent diameter of the alumina crystal and the ordinate being the number of alumina crystals. 4 shows the distribution range of the equivalent circle diameter of alumina crystals.

  Further, the skewness is an index indicating distribution asymmetry, and can be obtained using a function SKEW provided in Excel (registered trademark, Microsoft Corporation).

If the degree of strain is greater than 0, the number of alumina crystals having a circle-equivalent diameter smaller than the average circle-equivalent diameter of alumina crystals in the distribution curve of circle-equivalent diameters is a circle larger than the average circle-equivalent diameter of alumina crystals It means that the number is larger than the number of alumina crystals having an equivalent diameter.

  Therefore, if such a configuration is satisfied, the ratio of alumina crystals having a circle equivalent diameter smaller than the average circle equivalent diameter contributing to the reduction of irregular reflection of visible light is high, and thus the reflectance is further increased.

  The degree of skewness in the distribution curve of the equivalent circle diameter may be calculated from the data of the equivalent circle diameter of the alumina crystal obtained by the above-described measurement method.

  Next, a light source module provided with the ceramic reflector of the present disclosure will be described using FIG. Note that the light source module of the present disclosure is not limited to the configuration shown in FIG. 1, and provided that the ceramic reflector of the present disclosure is provided in a portion where high reflectance is required around the light source device. Good. In the light source module 10 shown in FIG. 1, the light source device 2 is positioned on the ceramic reflector 1 via the metal layer 3. The metal layer 3 may be used as an electrode or wiring.

  Since the light source module 10 of the example shown in FIG. 1 is provided with the ceramic reflector 1 of the present disclosure having high reflectance, it has high brightness while having high reliability.

  Next, a rotating body provided with the ceramic reflector of the present disclosure will be described with reference to FIG. In addition, a rotary body is a member, such as spherical shape and cylindrical shape which rotates. Specifically, it refers to a rotor, a shaft, a turbine or the like.

  As shown in FIG. 2, the rotating body 20 of the present disclosure includes a ceramic reflector 1 and a base 4, and at least a portion of the ceramic reflector 1 is exposed on the outer surface side of the base 4. Here, the ceramic reflector 1 and the base 4 have different color tones. For example, in the CIE 1976 L * a * b * color space, the ceramic reflective material 1 and the base 4 have a difference in lightness index L * of 10 or more. Further, FIG. 2 shows an example in which the ceramic reflecting material 1 is embedded in the base 4 so that a part thereof is exposed.

  And in the rotary body 20 of the present disclosure, the ceramic reflector 1 plays a role of reflecting the light emitted from the light measuring instrument 5, and the ceramic reflector 1 of the present disclosure has high reflectance. Because of this, when the measurement of the rotational speed or the like is performed using the light measuring instrument 5, accurate measurement results can be obtained, and the reliability is excellent.

  Further, the rotating body 20 of the present disclosure includes the ceramic reflector 1, the surrounding material 6 of the ceramic reflector 1, and the base 4, and at least a portion of the ceramic reflector 1 is exposed on the outer surface side of the base 4. The surrounding material 6 may be positioned so as to surround the exposed portion of the ceramic reflector 1.

  Here, the ceramic reflector 1 and the surrounding material 6 have different color tones. For example, in the CIE 1976 L * a * b * color space, the ceramic reflective material 1 and the surrounding material 6 have a difference in lightness index L * of 10 or more. If such a configuration is satisfied, when measuring the rotation speed and the like using the light measuring instrument 5, the ceramic reflective material 1 is noticeable by the surrounding material 6, and more accurate measurement results can be obtained.

In particular, if the surrounding material 6 exhibits a black color tone having a lightness index L * of 40 or less in the CIE 1976 L * a * b * color space, a ceramic reflection exhibiting a white color tone having a lightness index L * of 90 or more When the material 1 is noticeable due to the contrast with the surrounding material 6 and the light measurement device 5 is used to measure the rotation speed, a more accurate measurement result can be obtained.

  Here, the surrounding material 6 may be made of any material, but if it is made of alumina ceramic, the thermal expansion coefficients of the ceramic reflecting material 1 and the surrounding material 6 approximate each other. Since the cracks resulting from the difference in thermal expansion coefficient are less likely to occur, the rotating body 20 can be suitably used in an environment where the temperature changes rapidly.

  Next, an example of a method of manufacturing the ceramic reflector will be described.

First, alumina (Al ₂ O ₃ ) powder, silicon oxide (SiO ₂ ) powder as a sintering aid, calcium carbonate (CaCO ₃ ) powder and magnesium hydroxide (Mg (OH) ₂ ) powder are prepared.

  Here, as alumina powder, two types of alumina powder, an alumina raw material A with an average particle diameter of 0.2 μm, and an alumina raw material B with 1.0 μm, are prepared. The equivalent circle diameter of the alumina crystal can be controlled by changing the blending ratio. Specifically, alumina raw material A: alumina raw material B = 20 to 80: 80 to 20 in mass ratio may be used.

  Then, these two types of alumina powders are compounded in an appropriate ratio, and pulverized to a particle size of 0.3 μm or more and 0.9 μm or less measured by a laser diffraction / scattering method, to obtain a primary raw material powder. In addition, in the laser diffraction / scattering method, the particle diameter of aggregated particles in which a plurality of minute particles are aggregated is also measured, so the actual particle diameter of the alumina powder is better than the average particle diameter measured by the laser diffraction / scattering method. Will be small.

Then, of all components 100% by mass constituting the ceramic reflector, so that a value obtained by converting the Al to Al ₂ O ₃ becomes 98 mass% or more, the powder is the primary raw material powder and the sintering aids (Calcium carbonate powder, magnesium hydroxide powder and silicon oxide powder) are weighed.

  And 3 mass parts or more and 10 mass parts or less water soluble acrylic resin to a total of 100 mass parts of primary raw material powder, each powder which is sintering auxiliary agent, and each powder which is primary raw material powder and sintering auxiliary agent And a solvent such as 20 parts by mass or more and 60 parts by mass or less in a stirrer and mixed and stirred to obtain a slurry.

  Next, a sheet is formed by a doctor blade method using this slurry. Alternatively, a sheet is formed by a roll compaction method using granules obtained by spray granulation of the slurry with a spray granulator (spray dryer). In addition, there exist a press method, an extrusion method, the injection molding method etc. as a method of producing shapes other than a sheet | seat.

  Next, the sheet is processed by die pressing or laser processing to obtain a molded product having a predetermined product shape or a product approximate shape.

  Then, the obtained molded body is placed in a firing furnace in the atmosphere (oxidizing) atmosphere, and held and fired at a temperature of maximum temperature 1450 ° C. or more and 1550 ° C. or less for 0.1 hours or more and 5 hours or less. Get Thus, the relative density is 92% or more, and less than 0.2 μm is 3% or less in the equivalent circle diameter of the alumina crystal by firing the compact using the primary raw material powder of the above-mentioned crushed particle size at the highest temperature. More than 15%, 0.2 μm or more and 0.8 μm or less can be 55% or more and 80% or less, and more than 0.8 μm can be 15% or more and 40% or less.

Further, in the ceramic reflector of the present disclosure, the average equivalent circular diameter of alumina crystal is 0.5 μm.
In order to obtain m or more and 0.7 μm or less, the maximum temperature at the time of firing of the molded body may be 1480 ° C. or more and 1520 ° C. or less.

  Further, in order to make the circularity of the alumina crystal in the ceramic reflective material of the present disclosure to be 0.68 or more and 0.78 or less, the ground particle size measured by the laser diffraction / scattering method is 0.5 μm or more and 0.7 μm It may be crushed until it becomes below.

  Moreover, in order to make the distortion degree in the distribution curve of a circle equivalent diameter larger than 0 in the alumina crystal in the ceramic reflection material of the present disclosure, when blending the alumina raw material A and the alumina raw material B A large amount of raw material A may be blended.

  In addition, the surface of the sintered body obtained may be polished if necessary, and for example, the surface may have an arithmetic average roughness Ra of 0.3 μm or less by this polishing.

  Next, an example of a method of manufacturing the light source module of the present disclosure will be described. First, the ceramic reflector of the present disclosure is prepared. Then, a paste containing gold, silver, copper or a mixture of these is applied to the surface of the ceramic reflector by thick film printing, and heat treatment is performed to provide a metal layer. And the light source module of this indication can be obtained by arrange | positioning a light source device on a metal layer. Here, from the viewpoint of production efficiency, after the ceramic reflector is made to have a desired size and a metal layer is formed on the ceramic reflector, a rotating disk or the like in which industrial diamond is embedded is used so as to form pieces of the desired size. It may cut and divide.

  In addition, you may form a metal layer by well-known plating method, sputtering method, the active metal method etc. besides the method of forming with a paste.

  In addition, the surface of the metal layer may be plated partially or entirely. By performing the plating process in this manner, oxidation corrosion of the metal layer 3 can be suppressed. The type of plating may be any known plating, and examples thereof include gold plating, silver plating and nickel-gold plating.

  Examples of the present disclosure will be specifically described below, but the present disclosure is not limited to these examples.

First, alumina (Al ₂ O ₃ ) powder and silicon oxide (SiO ₂ ) powder, calcium carbonate (CaCO ₃ ) powder and magnesium hydroxide (Mg (OH) ₂ ) powder which are sintering aids were prepared.

  Here, as alumina powder, two types of alumina powder, an alumina raw material A with an average particle diameter of 0.2 μm, and an alumina raw material B with 1.0 μm, were prepared.

  Then, a primary raw material powder was obtained by blending and pulverizing these two types of alumina powders in an appropriate ratio.

Then, of all components 100% by mass constituting the ceramic reflector, so that a value obtained by converting the Al to Al ₂ O ₃ becomes 98 mass% or more, the powder is the primary raw material powder and the sintering aids (Calcium carbonate powder, magnesium hydroxide powder and silicon oxide powder) were weighed. The sintering aid is a silicon oxide powder, a calcium carbonate powder and a magnesium hydroxide powder such that the weight conversion ratio of SiO ₂ , CaO and MgO is SiO ₂ : CaO: MgO = 64: 5: 31. Weighed.

  And 6 parts by mass or less of a binder such as a water-soluble acrylic resin with respect to a total of 100 parts by mass of the primary raw material powder, each powder as a sintering aid, and each powder as a primary raw material powder and a sintering aid A slurry was obtained by putting 40 parts by mass of the solvent in a stirrer and mixing and stirring.

  Next, a sheet was formed by a doctor blade method using this slurry, and a plate-like formed body was obtained by die pressing. The proportions of the two types of alumina powder in each sample were adjusted to have the values shown in Table 1 in consideration of the sintering conditions. The ratio of the two types of alumina powder in 11 is mass ratio of alumina raw material A: alumina raw material B = 50: 50.

  And each sample was obtained by putting the obtained molded object in the baking furnace of air | atmosphere (oxidation) atmosphere, hold | maintaining and baking it at each sample desired maximum temperature for 1 hour. Sample No. The maximum temperature in 2, 3, 6, 7, 10 to 12 is in the range of 1450 ° C. or more and 1550 ° C. or less. 11 is 1490 ° C.

Next, using each of the obtained samples, the number ratio for each range of the circle equivalent diameter of the alumina crystal was calculated. First, each sample was polished and processed into a mirror surface. Then, with the surface polished to a mirror surface as a measurement surface, the measurement surface was observed at a magnification of 5000 using a scanning electron microscope and photographed with a CCD camera. Next, using the captured image, an image analysis software (Win ROOF Co., Ltd. Mitani Corp.) is used to make the measurement target an area of 413 μm ^{2 and} the equivalent circle diameter of the alumina crystal under the condition without threshold value. It measured and each number ratio of less than 0.2 micrometer, 0.2 micrometer or more and 0.8 micrometer or less, and 0.8 micrometer or more was computed.

  Next, the reflectance of each sample was measured. The measurement was performed using a spectrocolorimeter (color reader CR-13 manufactured by Konica Minolta) under the conditions of reference light source D65, wavelength range 360 to 740 nm, field of view 10 °, illumination diameter 3 × 5 mm, and measurement results The reflectance value of 500 nm was read from.

Next, relative density was determined for each sample by the Archimedes method. The results are shown in Table 1. In addition, for each sample, qualitative analysis is performed using XRF, quantitative analysis is performed using ICP for components other than Al, and as a result of subtracting the total of these from 100% by mass, all the samples are Al ₂ Al ₂ It is confirmed that the ceramic is an alumina-based ceramic containing 98% by mass or more in terms of O ₃ .

  Sample No. Relative density was 92% or more, and the reflectance in 500 nm was 92% or more with respect to the sample of 2, 3, 6, 7, 10-12. From these results, it was found that the ceramic reflector of the present disclosure has high reflectivity while having mechanical properties that can withstand use while being inexpensive.

  Next, it confirmed about the change of the reflectance by the average equivalent circular diameter of an alumina crystal. Sample No. Sample No. 15 in Example 1; Sample No. 11 is the same sample, and the other samples are sample No. It is a sample from which only 11 and a calcination temperature differ.

  With respect to the obtained sample, the average equivalent circle diameter of alumina crystals was calculated by the same method as the method of calculating the number ratio for each range of equivalent circle diameters of alumina crystals described in Example 1. Further, in the same manner as the method described in Example 1, a numerical value of reflectance of 500 nm was obtained. The results are shown in Table 2.

  Sample No. The values of reflectance of 15 to 17 were higher than those of the other samples. From this result, it was found that when the average equivalent circular diameter of the alumina crystal is 0.5 μm or more and 0.7 μm or less, the reflectance is further increased.

  Next, it confirmed about the change of the reflectance by circularity of an alumina crystal. Sample No. Sample No. 22 in Example 2. Sample No. 16 is the same sample, and the other samples are sample No. It is a sample from which the grinding | pulverization particle size of 16 and 2 types of alumina powder differs.

And each sample obtained was grind | polished and processed into the mirror surface. Next, with the surface polished to a mirror surface as a measurement surface, the measurement surface was observed at a magnification of 5000 using a scanning electron microscope and photographed with a CCD camera. Next, using the captured image, the image analysis software “image A (kun 2. ver.
52) ”(registered trademark, manufactured by Asahi Kasei Engineering Co., Ltd.) using the circularity 1; the lightness is bright, the small figure removal area is 0.002 μm, and the threshold is 100 which is an index indicating the brightness of the image. The analysis was performed, and the calculated circularity is shown in Table 3.

  Further, in the same manner as the method described in Example 1, a numerical value of reflectance of 500 nm was obtained. The results are shown in Table 3.

  Sample No. The values of reflectance of samples 20 to 22 were higher than those of the other samples. From this result, it was found that when the circularity of the alumina crystal is 0.68 or more and 0.78 or less, it is possible to have a higher reflectance.

1: Ceramics reflective material 2: Light source device 3: Electrode 4: Base 5: Light measuring instrument 6: Surrounding material 10: Light source module 20: Rotatable body

Claims (7)

Alumina ceramics containing alumina crystals and containing at least 98 mass% of Al in terms of Al ₂ O ₃ ,
Relative density is 92% or more,
In the equivalent circle diameter of the alumina crystal,
Less than 0.2 μm is 3% or more and 15% or less,
55% or more and 75% or less of 0.2 μm or more and 0.8 μm or less,
The ceramic reflector with a 0.8 μm excess of 15% to 40%.   The ceramic reflective material according to claim 1, wherein an average equivalent circle diameter of the alumina crystal is 0.5 μm or more and 0.7 μm or less.   The ceramic reflector according to claim 1, wherein the circularity of the alumina crystal is 0.68 or more and 0.78 or less.   The ceramic reflector according to any one of claims 1 to 3, wherein the alumina crystal has a strain degree in a distribution curve of equivalent circle diameters that is greater than zero.   A light source module comprising the ceramic reflector according to any one of claims 1 to 4. A ceramic reflector according to any one of claims 1 to 4, and a substrate having a color tone different from that of the ceramic reflector.
The rotating body wherein at least a portion of the ceramic reflector is exposed on the outer surface side of the base. A ceramic reflector according to any one of claims 1 to 4, a surrounding material of the ceramic reflector, and a substrate.
At least a part of the ceramic reflector is exposed on the outer surface side of the substrate,
The rotating member is positioned so as to surround the exposed portion of the ceramic reflector with a surrounding material different in color tone from the ceramic reflector.

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